Method of reducing metallic oxids.



No. 718,891. PATBNTED JAN. 20, 1903.

E. G. 'ACHBsxoNI METEO o RE ING METALLIC OXIDs.

' PLIGATIl ILBD DEO. 4, 1900. N0 MGDEL. 2 SHEETS-SHEET 1.

No. 718,891. PATENTED JAN. 20, 1903. E. G. ACHESON.

METHOD 0F REDUCING METALLIC OXIDS. APPLIUATIOH FILED DEU. 4, 1900.

No MODEL. 2 SHEETS-s111191' z.

WITNESSES INVENTOR operation.

UNITED STATES v .PAT-ENTI OFFICE..

EDWARD eooDRIcH lAcHEsoN, oF 'NIAGARA FALLS, NEW YORK.

METHOD oFV REDUCIN'G METArLlctoXlns.

srEcmcApTroN fqrmingpart ef Lettersretent No. 718,891, dated January 2o, 1903. I l Application'iiled December 4,1900. Serial No. 38.683. (Ndspecimens.) I

To ali whom, it ntcty concern:

Be it known that I, EDWARD GOODRICH 'ACBESON, of Niagara Falls, in the 'county of Niagara and State of New York, have invented anew and useful Methodoi;` Reducing Compoundsmf which the following is afnll; clear, and exact description, reference being had to -the 'accompanying drawings, forming part of` this'speciflcation, in which- Figure 1 shows in vertical longitudinal section an electric furnace. prepared for the practiceof my invention. Fig.V 2Vis asimilar View showing the furnace 4at the end of the Fig. 3 isa vertical cross-section on 4the 4line III III of Fig. 2. Fig.v 4 is a vertical cross-section of a modified construction,

showing the furnace before vthel beginning of the process.v V

-My invention relates, primarily, to thereduction of metallic compounds under .the

'influence -of electrically -sup-plied heat. vIt

`duringthe process, and having thus protected the conductor from contact with 'the material to betreated I heat 4such material by radial- 'tion' from the conductor and cause the de sired reactions'to take place.. The material to betreated consists of a mixture of the nieytallic oxid with a reducing agent, preferablyy carbon, and being shielded from lthe conductor is not aiected chemically thereby to any injurious extent.

' In the manufacture of substanoessuclias silicon or boron, which form refractory carbids, Irproceed as follows: 'W'hen the carbid sheath is to be formed during operation,

'I place in the furnace a conductor composed either of granules of carbon. orof carbon rods and surround it .with the material to be treated, which consists of the sand or other refractory oxid vmixed with carbon in about the proper proportions chemically to reduce itto elemental form. Where the conductor is 'plained 'be employed.

is made o-f-'granular carbon and the sheath orig-1f shieldis to :be formed of-the charge mixture, "i

the eiectof passi-ng a current of Aelectricity through the conductor-is to raise itzto anin`"- tense heat and tocause Athe charge mixture"v it, so as to form a layer of carbid of silicon, (when sand is'use'd inthe charge,) which in- 'immediately adjacent to it to combine with The heat being transmittedthrough the'shield raises the charge mixture to a high temperature." The carbon of the charge mixture then,

reactsV up'on the oxid, reducing it' to elemen` tal formand to 'a"s'tate,of fusion, causing it to sin-k to the bottom of the cayity whichis created in the charge mixture by the reduc-v tion; If the carbon conductor were not protected throughout the process by thecarbid, i.

it would'com bine chemically with or contaminate -t'he reducedV material. r

. 4Where the conductor for the'current is not composed of granular' carbon or where itis notl desirable that Athe'carbon core should. be

Sol.

wasted in the formation of the carbid shield, I may place'around. the conductor inlcontact therewith a layer of the oxid torb'e treated,

(or the oxidof any metal whose carbid is ref ract0ry mixed with carbon in suic'ientprca vp ortiongto combine therewith' iin the formv of a carbid.V '-T- he' first heating action .-of the current is thus expended iu.converti ngth1s layer into aprotecting-shield'ofrefractory I carbid, which protects the core, as above ex- In thedrawings, 4represents the walls ofan electric furnace. 3 3 aretlie termiing-core of carbon, whichy connects the terminals and is 0r maybe constitutedof granular coke, though rods-'or plates of-carbon may 5 is the body of charge mix'- tnre which surrounds the conductingfcore nals of the dynamo-circuit. .41is theconduct.-

and is composed of the ox'id 'to be reduced,

mixed with powdered carbon or other suitable reducing agent inthe well-known chem# Y ical proportion suitable for reduction;

Fig. 2 shows the furnaeeas it is at the end of the operation, 6 representing the? body of silicon or other reduced material which collects in a molten mass at the bottom of thecavity 7, which the reduction creates, and 8 represents the layer of carbid which constitutes the shield for the conductor and is of different nature from the cond-uctorand from the charge to be heated and which is rendered suiiiciently st-rong and dense during the process to uphold the conductor in place, even if the latter is made'ofvgranular carbon. At the end of the operation the reduced material having cooled into an aggregated crysformed refractory carbid, (for example, carbid of silicon or'carbd of boron,) preferably crushed to a finely-comminuted state, and I place the charge mixture around it. alumina is to be reduced, I mix alumina with f carbon in about the proportions` required chemically for its reduction tounetallic form. 'In Fig. 4 I show a layer`"'8 of carbid placed around the conductor when the furnace is charged. When the current is passed through the conductorsurrounded by crushed carbid, the heat created thereby recrys'tallizes and cements the layer Sinto a dense coherent tubular sheath, through which the heat is t-`rans.

mitted to the charge mixture, and the desired reactions take place in the manner above explained. The 'metallic aluminium when reduced will eollectat the bottom of the cavity 7, from which it may be taken either by tapping or by removing it as a pig at the end of the operation.

The electric current which I employ may I be alternating or direct and of a current density of, say, thirty amperes or more per square inch ofcross-section of conductor when the conductor is granular and of greater currentdensity when the conductor is made of rods or plates.

Care should be taken not to use a current density great enough to generate such a high degree of heat as to decompos'ethe carbid shield.

The incandescent furnacev is in man-)frespects the most eicient, easily-handled, and all-round useful design lfor' electric heating; but it has heretofore been seriously .limited by the reactions that take place between the conducting-core and the materials being operated upon. Efforts have been madel to overcome this diculty by interposing proj tecting-coatings, and for this purpose clay,

`c'orundum, andV other highly-.refractory materials have been used and found more or less efficient where the temperatures were not sufficient to cause the melting` of" the material of which they were formed Ior, as sometimes Wheremy hand.

occurs, their reduction where they are in coi tact with the carbon conducting-core. Another ditculty that inventorshave sought to overcome is the tendency of the current to leave the properly-prepared conducting-core and pass through the materials being operated upon Where they form more or less of a conducting mass.- To corirect this diiculty, Various materials have been suggestedsuch as clays, oxids, and in some instances finelypowdered carbon or charcoal on account of their relatively high resiste uce qualityas 1s suggested by Elihu Thomson in his Patent No. 513,602. Allof these attempts have been more or less successful, but have not met the conditions as met by my discovery, that carbid of silicon might be used for the double purpose of preventing chemical react-ion between the carbon core and the charge of th'e furnace and also largely assist ininsulating the surrounding charge in order that the current might be more thoroughly confined to the prepared conductingcore. Carbid of silicon is'stable at the highest temperatures ordinarily'desired for metallurgical operatons',and the silicon being already thoroughly satisfied no reaction occurs between it and the conducting-core. I have also discovered that it is inert at high temperatures While in contact with many materials it is desired to reduce, melt, or smelt in the electric furnace. l

Vithin the scope of my invention as defined in the claims the process maybe modilied to suit the conditions of the particular material treated thereby, since 1. The method of reducing metallic compounds, which consists in passing an electric current through an electrical conductor placed in proximity to the compound to be treated and shielded therefrom by'a body of refractory carbid; substantially as described.

2. The method of reducing metallic oxids 'which consists in passing an electric current through an electrical conductor placed in .proximity to the oxid to be treated, together with carbon in proper proportion to reduce the oxid to its elemental state, and shielded therefrom by a body of carbid, substantially as described.

3. The method of reducing metallic oxids,l which consists in placing in proximity to an roo IIO

electric conductor the oxid to be treated mixed.

with a reducing agent in proper proportion to reduce the oxid to its elemental state, placing betweenthe conductor and such mixture a layer ofpreformed refractory carbid, and passing an electric current through the conductor; substantially as described.

las

In testimony whereof Ihave hereunto set i EDWARD GOGDRICII ACHESON. WVitnesses:

J oHN MILLER, L. M. REDMAN, 

